Dual damascene interconnect process with borderless contact

Abstract

A dual damascene process is disclosed for forming contact and via interconnects without borders. A nitride layer is first formed on a dielectric layer to function as a hard-mask. Metal line trench is first etched into the nitride layer and then into the dielectric layer. Then, a second photoresist layer is used to pattern contact or via hole over line trench opening and the dielectric layer is further etched through the line trench into the dielectric layer until the substructure of the substrate is reached. It is disclosed that by using the nitride layer as a hard-mask, the registration or alignment tolerance between the contact/via hole pattern and the metal line pattern can be relaxed substantially and not use a border as is conventionally practiced in order to assure proper registration between the patterns. The borderless interconnect is achieved by filling the composite line opening and the hole opening with metal and chemical mechanical polishing. The process enables cost reduction and productivity in the semiconductor manufacturing line.

What is claimed is: 
     
       1. A method of forming a self-aligned, borderless contact comprising the steps of: providing a semiconductor substrate having a substructure comprising devices formed in said substrate;   forming an interlevel dielectric (ILD) layer over said substrate;   performing chemical mechanical polishing of said ILD layer;   forming an hard-mask layer over said ILD layer;   forming a first photoresist layer over said hard-mask layer;   patterning said first photoresist layer with a metal line pattern;   etching through said metal line pattern in said first photoresist layer into said hard-mask layer;   etching further said metal line pattern into said ILD layer;   removing said first photoresist layer from said substrate;   forming a second photoresist layer over said substrate including said metal line opening;   patterning said second photoresist layer with a contact hole pattern;   etching through said contact hole pattern in said second photoresist layer into said ILD layer until a lower level said substructure of said substrate is reached;   removing said second photoresist layer;   forming a glue layer over said substrate including said metal line and contact hole opening forming a composite opening;   forming metal in said composite opening in said ILD layer; and   removing said metal from the surface of said substrate for subsequent process steps to complete the fabrication of a semiconductor substrate.   
     
     
       2. The method of claim 1, wherein said ILD layer comprises plasma enhanced tetraethyl orthosilicate (PETEOS). 
     
     
       3. The method of claim 1, wherein said ILD layer has a thickness between about 8000 to 10000 Å. 
     
     
       4. The method of claim 1, wherein said forming an hard-mask layer over said ILD layer is accomplished by reacting dichlorosilane (SiCl 2  H 2 ) with ammonia (NH 3 ) in an LPCVD at a pressure between about 0.01 to 0.05 torr, temperature between about 700 to 900° C. 
     
     
       5. The method of claim 1, wherein said first photoresist layer over said ILD layer has a thickness between about 0.6 to 1.0 micrometers (μm). 
     
     
       6. The method of claim 1, wherein said patterning said first photoresist layer is accomplished with a mask having said metal line pattern. 
     
     
       7. The method of claim 1, wherein said etching through said metal line pattern in said first photoresist layer into said hard-mask layer is accomplished with a recipe comprising SF 6  and He. 
     
     
       8. The method of claim 1, wherein said etching further said metal line pattern into said ILD layer is accomplished with a recipe comprising CF 4 , CHF 3  and Ar. 
     
     
       9. The method of claim 1, wherein said first photoresist layer is removed by oxygen ashing. 
     
     
       10. The method of claim 1, wherein said second photoresist layer over said substrate including said metal line opening has a thickness between about 0.3 to 0.8 μm. 
     
     
       11. The method of claim 1, wherein said patterning said second photoresist layer is accomplished with a mask having said contact hole pattern. 
     
     
       12. The method of claim 1, wherein said etching through said contact hole pattern in said second photoresist layer into said ILD layer until said substructure of said substrate is reached is accomplished with a recipe comprising gases CH 2  F 2  and C 4  F 8 . 
     
     
       13. The method of claim 1, wherein said removing said second photoresist layer is accomplished with oxygen ashing. 
     
     
       14. The method of claim 1, wherein said depositing a glue layer over said substrate including said metal line and contact hole opening forming a composite opening is accomplished by depositing Ti or TiN. 
     
     
       15. The method of claim 1, wherein said forming metal in said composite opening in said ILD layer is accomplished by depositing tungsten. 
     
     
       16. The method of claim 15, wherein said removing said metal from the surface of said substrate is accomplished by chemical mechanical polishing. 
     
     
       17. A method of forming a self-aligned, borderless via comprising the steps of: providing a semiconductor substrate having a substructure comprising metal layers formed in said substrate;   forming an intermetal dielectric (IMD) layer over said substrate;   performing chemical mechanical polishing of said IMD layer;   forming an hard-mask layer over said IMD layer;   forming a first photoresist layer over said hard-mask layer;   patterning said first photoresist layer with a metal line pattern;   etching through said metal line pattern in said first photoresist layer into said hard-mask layer;   etching further said metal line pattern into said IMD layer;   removing said first photoresist layer from said substrate;   forming a second photoresist layer over said substrate including said metal line opening;   patterning said second photoresist layer with a via hole pattern;   etching through said via hole pattern in said second photoresist layer into said IMD layer until a lower level said substructure of said substrate is reached;   removing said second photoresist layer;   forming a glue layer over said substrate including said metal line and via hole opening forming a composite opening;   forming metal in said composite opening in said IMD layer; and   removing said metal from the surface of said substrate for subsequent process steps to complete the fabrication of a semiconductor substrate.   
     
     
       18. The method of claim 17, wherein said IMD layer comprises plasma enhanced tetraethyl orthosilicate (PETEOS). 
     
     
       19. The method of claim 17, wherein said IMD layer has a thickness between about 8000 to 10000 Å. 
     
     
       20. The method of claim 17, wherein said forming an hard-mask layer over said IMD layer is accomplished by reacting dichlorosilane (SiCl 2  H 2 ) with ammonia (NH 3 ) in an LPCVD at a pressure between about 0.01 to 0.05 torr, temperature between about 700 to 900° C. 
     
     
       21. The method of claim 17, wherein said first photoresist layer over said IMD layer has a thickness between about 0.6 to 1.0 micrometers (μm). 
     
     
       22. The method of claim 17, wherein said patterning said first photoresist layer is accomplished with a mask having said metal line pattern. 
     
     
       23. The method of claim 17, wherein said etching through said metal line pattern in said first photoresist layer into said hard-mask layer is accomplished with a recipe comprising SF 6  and He. 
     
     
       24. The method of claim 17, wherein said etching further said metal line pattern into said IMD layer is accomplished with a recipe comprising CF 4 , CHF 3  and Ar. 
     
     
       25. The method of claim 17, wherein said first photoresist layer is removed by oxygen ashing. 
     
     
       26. The method of claim 17, wherein said second photoresist layer over said substrate including said metal line opening has a thickness between about 0.3 to 0.8 Å. 
     
     
       27. The method of claim 17, wherein said patterning said second photoresist layer is accomplished with a mask having said via hole pattern. 
     
     
       28. The method of claim 17, wherein said etching through said via hole pattern in said second photoresist layer into said IMD layer until said substructure of said substrate is reached is accomplished with a recipe comprising gases CH 2  F 2  and C 4  F 8 . 
     
     
       29. The method of claim 17, wherein said removing said second photoresist layer is accomplished with oxygen ashing. 
     
     
       30. The method of claim 17, wherein said depositing a glue layer over said substrate including said metal line and via hole opening forming a composite opening is accomplished by depositing Ti or TiN. 
     
     
       31. The method of claim 17, wherein said forming metal in said composite opening in said IMD layer is accomplished by depositing tungsten. 
     
     
       32. The method of claim 17, wherein said removing said metal from the surface of said substrate is accomplished by chemical mechanical polishing.